Presently, several systems interacting with a user in order to aid the user in reaching a certain physiological state or aiding the user in order to achieve certain goals related to physical exercise are known. As an example, biofeedback devices are on the market, which monitor the physiological state of the user via sensors and use music or sounds as feedback to the user in order to facilitate the user falling into the sleep state. Such systems may be bulky and expensive and may not be portable. One other drawback may be they are basically constructed to perform only function, i.e. the biofeedback.
Apart from biofeedback and portable feedback systems, known portable measurement devices may monitor physiological parameters, such the already mentioned heart rate, muscle tension, pulse, temperature and other parameters.